Supersize: Store whether source path was generated in flags

tools/binary_size/libsupersize/testdata/Diff_Basic.golden

 Common Metadata:
     baz=yes
     foo=1
 Old Metadata:
     bar=[1, 2, 3]
 New Metadata:
     bar=[1, 3]
 
 Section Sizes (Total=0 bytes):
     .bss: 0 bytes (not included in totals)
@@ skipping 60 matching lines @@
                source_path=     object_path=
                flags={}  name=** symbol gaps
 =       82 r@Group      pss=0  padding=0  size_without_padding=0  count=2
                source_path=     object_path=
                flags={}  name=** symbol gaps
 =       82 d@0x2cd84e0  pss=0  padding=0  size_without_padding=0
                source_path=     object_path=third_party/gvr-android-sdk/libgvr_shim_static_arm.a/libcontroller_api_impl.a_controller_api_impl.o
                flags={}  name=.Lswitch.table.45
 =       82 d@0x2c176f0  pss=0  padding=0  size_without_padding=0
                source_path=third_party/icu/ucnv_ext.c   object_path=third_party/icu/icuuc/ucnv_ext.o
-               flags={}  name=ChromeMainDelegate [vtable]
+               flags={gen}  name=ChromeMainDelegate [vtable]
 =       82 d@0x2cd8500  pss=0  padding=0  size_without_padding=0
                source_path=third_party/paint.cc         object_path=third_party/WebKit.a/PaintChunker.o
                flags={}  name=ChromeMainDelegateAndroid [vtable]
 =       82 r@0x284e370  pss=0  padding=0  size_without_padding=0
                source_path=base/page_allocator.cc       object_path=base/base/page_allocator.o
                flags={}  name=Name
 =       82 t@0x28f1c8   pss=0  padding=0  size_without_padding=0
                source_path=third_party/icu/ucnv_ext.c   object_path=third_party/icu/icuuc/ucnv_ext.o
-               flags={startup}  name=_GLOBAL__sub_I_SkDeviceProfile.cpp
+               flags={startup,gen}  name=_GLOBAL__sub_I_SkDeviceProfile.cpp
 =       82 t@0x28d948   pss=0  padding=0  size_without_padding=0
                source_path=base/page_allocator.cc       object_path=base/base/page_allocator.o
                flags={startup}  name=_GLOBAL__sub_I_pacing_sender.cc
 =       82 d@0x2de70a4  pss=0  padding=0  size_without_padding=0
                source_path=third_party/container.c      object_path=third_party/WebKit.a/ContiguousContainer.o
                flags={anon,rel.loc}  name=base::android::g_library_version_number
 =       82 d@0x2de70a0  pss=0  padding=0  size_without_padding=0
                source_path=third_party/container.c      object_path=third_party/WebKit.a/ContiguousContainer.o
                flags={anon}  name=base::android::g_renderer_histogram_code
 =       82 d@0x2de7008  pss=0  padding=0  size_without_padding=0
@@ skipping 14 matching lines @@
 =       82 t@0x2a0010   pss=0  padding=0  size_without_padding=0
                source_path=third_party/paint.cc         object_path=third_party/WebKit.a/PaintChunker.o
                flags={}  name=blink::ContiguousContainerBase::shrinkToFit [clone .part.1234] [clone .isra.2]
                           full_name=blink::ContiguousContainerBase::shrinkToFit() [clone .part.1234] [clone .isra.2]
 =       82 t@0x2a1000   pss=0  padding=0  size_without_padding=0
                source_path=third_party/container.c      object_path=third_party/WebKit.a/ContiguousContainer.o
                flags={anon}  name=blink::PaintChunker::releasePaintChunks [clone .part.1]
                           full_name=blink::PaintChunker::releasePaintChunks() [clone .part.1]
 =       82 d@0x2c17728  pss=0  padding=0  size_without_padding=0
                source_path=third_party/icu/ucnv_ext.c   object_path=third_party/icu/icuuc/ucnv_ext.o
-               flags={}  name=chrome::mojom::FieldTrialRecorder [vtable]
+               flags={gen}  name=chrome::mojom::FieldTrialRecorder [vtable]
 =       82 d@0x2c17740  pss=0  padding=0  size_without_padding=0
                source_path=third_party/container.c      object_path=third_party/WebKit.a/ContiguousContainer.o
                flags={}  name=chrome::mojom::FieldTrialRecorderProxy [vtable]
 =       82 r@0x284e398  pss=0  padding=0  size_without_padding=0
                source_path=third_party/container.c      object_path=third_party/WebKit.a/ContiguousContainer.o
                flags={}  name=chrome::mojom::FilePatcher::Name_
 =       82 t@0x28d98a   pss=0  padding=0  size_without_padding=0
                source_path=base/page_allocator.cc       object_path=base/base/page_allocator.o
                flags={}  name=extFromUUseMapping
                           full_name=extFromUUseMapping(aj, int)
 =       82 t@0x28f1e0   pss=0  padding=0  size_without_padding=0
                source_path=third_party/icu/ucnv_ext.c   object_path=third_party/icu/icuuc/ucnv_ext.o
-               flags={unlikely}  name=foo_bar
+               flags={unlikely,gen}  name=foo_bar
 =       82 d@0x2de7000  pss=0  padding=0  size_without_padding=0
                source_path=base/page_allocator.cc       object_path=base/base/page_allocator.o
                flags={}  name=google::protobuf::internal::pLinuxKernelCmpxchg
 =       82 d@0x2de7004  pss=0  padding=0  size_without_padding=0
                source_path=third_party/container.c      object_path=third_party/WebKit.a/ContiguousContainer.o
                flags={}  name=google::protobuf::internal::pLinuxKernelMemoryBarrier
 =       82 r@0x28f3450  pss=0  padding=0  size_without_padding=0
                source_path=third_party/paint.cc         object_path=third_party/WebKit.a/PaintChunker.o
                flags={anon}  name=kAnimationFrameTimeHistogramClassPath
 =       82 d@0x2cd8550  pss=0  padding=0  size_without_padding=0
                source_path=base/page_allocator.cc       object_path=base/base/page_allocator.o
                flags={}  name=kMethodsAnimationFrameTimeHistogram
 =       82 d@0x2cd84f0  pss=0  padding=0  size_without_padding=0
                source_path=     object_path=third_party/gvr-android-sdk/libgvr_shim_static_arm.a/libport_android_jni.a_jni_utils.o
                flags={anon}  name=kSystemClassPrefixes
 =       82 d@0x2cd8538  pss=0  padding=0  size_without_padding=0
                source_path=base/page_allocator.cc       object_path=base/base/page_allocator.o
                flags={}  name=mojo::MessageReceiver [vtable]
 =       82 t@0x28f000   pss=0  padding=0  size_without_padding=0
                source_path=third_party/icu/ucnv_ext.c   object_path=third_party/icu/icuuc/ucnv_ext.o
-               flags={}  name=ucnv_extMatchFromU
+               flags={gen}  name=ucnv_extMatchFromU
                           full_name=ucnv_extMatchFromU(int const*, int, unsigned short const*, int, unsigned short const*, int, unsigned int*, signed char, signed char)
 -       82 b@0x2dffda0  pss=-28  padding=0  size_without_padding=-28
                source_path=third_party/icu/ucnv_ext.c   object_path=third_party/icu/icuuc/ucnv_ext.o
-               flags={}  name=g_chrome_content_browser_client
+               flags={gen}  name=g_chrome_content_browser_client
 -       82 b@0x2dffe80  pss=-4  padding=-196  size_without_padding=192
                source_path=third_party/icu/ucnv_ext.c   object_path=third_party/icu/icuuc/ucnv_ext.o
-               flags={}  name=SaveHistogram::atomic_histogram_pointer
+               flags={gen}  name=SaveHistogram::atomic_histogram_pointer
                           full_name=SaveHistogram(_JNIEnv*, base::android::JavaParamRef<_jobject*> const&, base::android::JavaParamRef<_jstring*> const&, base::android::JavaParamRef<_jlongArray*> const&, int)::atomic_histogram_pointer
 -       82 b@0x2dffe84  pss=-4  padding=0  size_without_padding=-4
                source_path=third_party/icu/ucnv_ext.c   object_path=third_party/icu/icuuc/ucnv_ext.o
-               flags={anon}  name=g_AnimationFrameTimeHistogram_clazz
+               flags={anon,gen}  name=g_AnimationFrameTimeHistogram_clazz
 =       82 b@0x0        pss=0  padding=0  size_without_padding=0
                source_path=third_party/fft_float.cc     object_path=third_party/ffmpeg/libffmpeg_internal.a/fft_float.o
                flags={}  name=ff_cos_131072
 =       82 b@0x0        pss=0  padding=0  size_without_padding=0
                source_path=third_party/fft_fixed.cc     object_path=third_party/ffmpeg/libffmpeg_internal.a/fft_fixed.o
                flags={}  name=ff_cos_131072_fixed
 =       82 b@0x0        pss=0  padding=0  size_without_padding=0
                source_path=third_party/fft_float.cc     object_path=third_party/ffmpeg/libffmpeg_internal.a/fft_float.o
                flags={}  name=ff_cos_65536